CODEWITHSUNDEEP
javaarraysobjectinteger
apparatix
apparatix

Reputation: 1512

Get the type of array element in Java

I have the following method:

public static int arraySum(Object obj) {
}

The method should return the sum of all elements in obj; a precondition for this method is that obj be an Integer array of any dimension, i.e. Integer, Integer[], Integer[][], so on.

In order to write the body of the method arraySum(), I'm using a foreach loop and recursion; however, for the foreach loop I need to know which type the elements of obj are. Is there a way to find out the type (i.e. Integer, Integer[], etc.) of obj?

EDIT: This is for an assignment for my CS course. I don't want to simply ask how to write the method, that's why I'm asking such a specific question.

Upvotes: 3

Views: 124

Answers (2)

ilalex
ilalex

Reputation: 3078

You can do it with simple instanceof, for example:

if (obj instanceof Integer[][]) 
    System.out.println("2d");
if (obj instanceof Integer[]) 
    System.out.println("1d");
if (obj instanceof Integer) 
    System.out.println("0d");

Upvotes: 0

arshajii
arshajii

Reputation: 129497

I believe it's simpler than you think:

public static int arraySum(Object obj) {
    if (obj.getClass() == Integer.class)
        return ((Integer) obj).intValue();

    int sum = 0;
    for (Object o : (Object[]) obj)
        sum += arraySum(o);

    return sum;
}

Basically we exploit the fact that an Integer array of any dimension is still an Object[].

Object obj = new Integer[][][]{{{1,2,3}},{{4,5,6},{7,8,9}},{{10}}};

System.out.println(arraySum(obj));

55

Upvotes: 7

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